At this age, sleep patterns in a child will keep changing and evolving until she is at least ... 5? 6? Or more. So don't be surprised when the pattern changes. You'll all just have to readapt.

Secondly, contrary to popular belief, the MORE a baby sleeps, the MORE she will sleep. Lack of naps in the day causes hormonal/chemical imbalances in the body that disturb the child's ability to sleep at night, thus causing them to enter wakefulness more often. The adult idea that denying a child sleep during the day will cause her to be more "tired" and sleep "more" at night is not only incorrect, it actually affects the child's development and mood.

Is she hungry when she wakes up? If so, it could be a temporary growth spurt, a short period of intense hunger.

I hope this helps; if not, give us more clues and details, no matter how trivial!